Animal Kingdom: Biology, Classification, Topics, Overview & MCQs
The animal kingdom is a group of living things that includes all animals. These are multicellular organisms that cannot make their food (heterotrophic) and depend on other living things for energy. They can move from one place to another and have different shapes, sizes, and body structures. The animal kingdom classification varies from simple sponges to complex mammals classified based on common characteristics and evolutionary relationships.
- Structural Organisation in Animals
- Animal Kingdom Classification
- Structural Organisation Levels in Animals
- Body Symmetry in Animals
- Organ System Patterns in Animals
- Animal Kingdom NEET MCQs
- Recommended Video On Animal Kingdom
Animal cells are eukaryotic and do not have rigid cell walls. This article includes structural organisation in animals, 11 phyla of the kingdom Animalia, and key features like body symmetry, type of organisation level, and organ system patterns such as the digestive and circulatory systems.
Structural Organisation in Animals
The structural organisation in animals explains how animals' bodies are built and function, from simple to complex forms. It ranges from unicellular organisms like protozoa to highly developed vertebrates. This organisation helps animals survive, adapt, and carry out life processes effectively.
Protozoa
Protozoa are often considered the simplest form of animals. These are a type of eukaryotic organism that is unicellular and has certain animal-like features like movement and predation. Protozoa eat through osmotrophy, which involves absorbing nutrients through cell membranes, or phagocytosis, which involves engulfing food particles with the help of pseudopodia.
Bryozoans
Bryozoans are typically thought of as moss animals. They are filter feeders that use a crown of tentacles laced with cilia to sieve food particles out of the water. They live in humid environments, glacial waters, and marine trenches. The majority are colonial (live in groups), with one genre being solitary (lives and functions independently). Individuals in bryozoans are called zooids, and they are not totally self-contained species. In the colony, autozooids are the specialized zooids responsible for feeding and excretion. Each zooid works together with others to support the survival of the whole colony.
Vertebrates
Vertebrates are animals with a backbone. This group includes jawed and jawless fish, amphibians, reptiles, birds, and mammals.
Fish like sharks and rays live in water.
Amphibians (e.g., frogs) live on land but reproduce in water.
Reptiles have dry skin covered with scales or scutes.
Aves are covered with feathers, have lightweight bodies, and are adapted for flight.
Mammals can live on land or in water, or fly. They have hair and produce milk.
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Animal Kingdom Classification
The 11 phyla of the animal kingdom are the major divisions that classify animals on the basis of body structure, complexity, and history of evolution.
Phylum | Description |
Porous bodies, multicellular animals designated as sponges, which have no proper tissues and organs. | |
Aquatic animals exhibiting radial symmetry and possessing specialized stinging cells, the cnidocytes. | |
Exclusively marine ciliated comb plates that help in movement and show bioluminescence, meaning they can produce light. | |
These are the flatworms, which include planarians and tapeworms. The body is dorso-ventrally flat and bilaterally symmetrical with no true coelom. | |
Roundworms with elongated, cylindrical bodies, which vary in habitats and are more often free-living or parasitic. | |
Segmented worms found in earthworms and leeches, annotated for having bodies segmented by a true coelom. | |
The largest phylum, including insects, arachnids, and crustaceans, are distinguished through having exoskeleton, jointed appendages, and segmented bodies. | |
A phylum of animals including snails, clams, and octopuses with a soft body often covered with a shell of hard chitinous material and a muscular foot. | |
Marine animals such as sea stars and sea urchins are examples of animals that have radial symmetry and an odd water vascular system. | |
Marine worms with a stomochord and pharyngeal gill slits; they are the closest relatives to chordates. | |
It includes animals that at some stage of their development have a notochord; an example is vertebrates, including mammals, birds, and fish. Other closely related invertebrates belong to the same class. |
Structural Organisation Levels in Animals
The animal tissues help in performing different life functions efficiently. From loosely arranged cells in sponges (cellular level) to fully developed organ systems in chordates (organ system level), animals show a gradual increase in complexity. These levels include cellular, tissue, organ, and organ system levels:
Cellular Level of Organisation | At this level, animals are made up of loosely arranged cells. These cells do not form tissues or organs. Example: Sponges (Porifera). |
Tissue Level of Organisation | Similar cells come together to perform a specific function and form tissues. There are no organs yet. Example: Coelenterates like Hydra. |
Organ Level of Organisation | The different types of tissues combine to form organs, and each organ performs a specific function. Example: Platyhelminthes (flatworms). |
Organ System Level of Organisation | This is the advanced level where organs work together to form organ systems, each with a specific physiological function (like digestion, circulation, etc.). Example: Annelids, Arthropods, Molluscs, Echinoderms, and Chordates. |
Body Symmetry in Animals
The symmetry in animals refers to how their body parts are arranged around a central point or line. It helps in understanding the shape, structure, and movement of different animals.
Asymmetrical: Animals that cannot be divided into two equal halves in any plane. Example: Sponges.
Radial Symmetry: The body can be divided into equal halves in any plane passing through the central axis. Example: Coelenterates, Ctenophores, Echinoderms.
Bilateral Symmetry: The body can be divided into equal left and right halves through only one plane. Example: Platyhelminthes, Annelids, Arthropods, Chordates.
Organ System Patterns in Animals
The variations in organ systems in different animals are described below:
Circulatory System: There are two types of circulatory systems, open and closed.
Open Circulatory System: Blood is not enclosed in vessels and flows freely in the body cavities. Example: Arthropods and Molluscs.
Closed Circulatory System: Blood flows via a series of vessels called capillaries, arteries, and veins in this type of circulatory system. Example: Annelids and Chordates.
Digestive system: The digestive system is divided into two categories. There are two types of digestive systems: complete and incomplete.
Complete Digestive System: There are two opening to the outside of the body in this sort of digestive system, a back end (anus) and a mouth. Example: Arthropods, Chordates.
Incomplete Digestive System: There is only one opening to the outside of the body, which functions as both the back end and the mouth. Example: Platyhelminthes.
Animal Kingdom NEET MCQs
Animal Kingdom is an important chapter for NEET aspirants as many questions are asked from here. Animal kingdom NEET questions practice and solving animal kingdom MCQs daily or almost daily boosts up the speed along with accuracy. Some frequently asked question types are:
Match the phyla with examples
Features of animal body plans
Relevance of the categories to evolution
Since these questions also check the conception of the subject and retention, Animal kingdom NEET MCQ practice is a must.
1. Which of the following is a characteristic feature of Phylum Annelida?
a) Radial symmetry
b) Jointed appendages
c) Segmented body
d) Pseudocoelom
Ans: c) Segmented body
2. In which of the following animal groups does the notochord remain throughout life?
a) Mammals
b) Amphibians
c) Protochordates
d) Reptiles
Ans: c) Protochordates
3. Which phylum includes organisms with radial symmetry and a water vascular system?
a) Arthropoda
b) Annelida
c) Echinodermata
d) Mollusca
Ans: c) Echinodermata
4. Which class of Arthropoda is known for having three pairs of legs?
a) Crustacea
b) Arachnida
c) Myriapoda
d) Insecta
Ans: d) Insecta
5. Which one of the following is NOT a feature of class Mammalia?
a) Mammary glands
b) Exoskeleton made of chitin
c) Three middle ear bones
d) Presence of hair or fur
Ans: b) Exoskeleton made of chitin.
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Recommended Video On Animal Kingdom
Frequently Asked Questions (FAQs)
5 characteristics of the animal kingdom are as follows:
Animals have several cells.
Animals are heterotrophic, meaning they get their energy from food that releases energy.
Sexual reproduction is the norm for animals.
Animals are composed of cells without cell walls.
Animals have the ability to move at some point in their lives.
Class insecta have the largest number of animals.
The 11 phyla of the animal kingdom are: Porifera, Cnidaria, Ctenophora, Platyhelminthes, Aschelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, Hemichordata, and Chordata.
All vertebrates (animals having a backbone) and a few invertebrates belong to the Phylum Chordata, which is part of the Kingdom Animalia (organisms without a backbone).
Vertebrates: Vertebrates are animals with a vertebral column and/or a notochord at some point throughout their existence.
Phylum Chordata – Phylum Chordata is a subclass of the Kingdom Animalia that includes both backboned animals and non-backboned creatures.
The notochord is only found in the larval tail area of some chordates. The notochord can be found in a variety of chordates throughout the body. The notochord is replaced by the vertebral column in some chordates. As a result, not all chordates are classified in the same way.
The largest phylum in the animal kingdom is Arthropoda. Ex- creatures like insects, spiders, crabs, and lobsters
- Oviparous: Animals that lay eggs - fertilization outside the body.
- Viviparous: Animals that give birth to live young - development inside the female womb.
Aschelminthes is also known as roundworms or nematodes.
Animals are classified based on several features:
- Cellular level of organization- cellular, tissue, organ, organ system
- Symmetry- asymmetrical, radial, bilateral
- Body cavity- coelom, pseudocoelom, acoelomate
- Germ layers- diploblastic, triploblastic
- Notochord - presence or absence
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